Haha fair enough. If you're in Mumbai, you can try the three staple street foods: vadapav, pani puri and pav bhaji. Then there's naan + butter chicken and chole bature, which would be the most popular foods from North India. And finally, dosa + sambhar if you want a taste of South India.
If you go to Colaba, there's great restaurants for everything I've mentioned above. Just search "fast food" or "north Indian" or "south Indian" on Google maps when you get there, and pick a popular one. Colaba (and south Mumbai in general) has most of the iconic attractions of the city, because it is the original part of the city.
Street shopping is big in the local culture too, so you can try this at Colaba causeway. Women really like shopping there, they always pick up pieces of clothing, jewelry or some small pieces of memorabilia.
If you're in North Mumbai, try going in the autorickshaws. I've seen a lot of foreigners think of it as a fun and unique experience, so I think you'd enjoy that as well. Mumbai is the only city in India where you don't have to negotiate with the driver of the autorickshaw, so keep this in mind and only pay them the fare shown on the meter.
And if you want to complete your Mumbai experience, try the local train. You might not be used to the crowds, so try to go during off-peak hours: 7-10 AM from North to South Mumbai and 5-7 PM from South to North Mumbai will be the most crowded times. There's an app called UTS where you can book tickets, and an app called m-indicator that you can see the train schedule of each station.